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| Endocrine system |
Gland: An organ that produces substances (hormones, enzymes, sebum, milk, etc.) needed by the body and secretes them into ducts or directly into the bloodstream.
Types of Glands:
Exocrine Glands: Glands that secrete substances (enzymes, sebum, milk, sweat, saliva, etc) into the ducts.
Ex: sweats glands (sweat), sebaceous glands (sebum), salivary glands (saliva), mammary glands (milk), pancreas (pancreatic enzyme), liver, etc.
Endocrine Glands: Ductless glands that secrete substances (hormones) directly into the bloodstream.
Hormones: Hormones are secreted directly into the bloodstream and then carried throughout the body where they influence only those cells that have receptors for the hormone. Hormone (chemical messenger) can only act on target cells. Chemically, hormones are steroids, amines, or proteins.
Endocrine System: A group of endocrine glands that produce and secrete hormones. It regulates the body's growth, metabolism, sexual development, and function.
Major glands of the Endocrine System: Hypothalamus, Pituitary gland, Thyroid gland, Parathyroid gland, Adrenal gland, Gonads (testes and ovaries), Endocrine part of the pancreas, Thymus gland, and Pineal gland.
Hypothalamus: A region in the brain, located under the thalamus, acts as a link between the Nervous System and Endocrine System. The hypothalamus controls secretions of the pituitary gland via releasing or inhibiting factors.
Hormones released/inhibited by Hypothalamus:
1. GHRH (Growth Hormone Releasing Hormone) - Stimulates secretion of GH (Growth Hormone) by the Pituitary gland.
2. GnRH (Gonadotropin-Releasing Hormone) - Stimulates secretion of FSH and LH by the Pituitary gland.
3. TRH (Thyrotropin Releasing Hormone) - Stimulates secretion of TSH (Thyroid Stimulating Hormone) by the Pituitary gland.
4. CRH (Corticotropin-Releasing Hormone) - Stimulates secretion of ACTH (Adrenocorticotropic Hormone) by the Pituitary gland.
5. SS (Somatostatin) - Inhibits secretion of GH (Growth Hormone) by the Pituitary gland.
6. DA (Dopamine) - Inhibits secretion of Prolactin by the pituitary gland.
Pituitary gland / Hypophysis: A small pea-sized gland located in Sella Turcica. It is called as Master gland as it controls all other glands.
Regions of Pituitary gland: 1. The anterior lobe of the Pituitary gland (Adenohypophysis). 2. Posterior lobe of the Pituitary gland (Neurohypophysis).
Activities of Pituitary gland regions: Activity of the Adenohypophysis is controlled by releasing hormones from the Hypothalamus Activity of the Neurohypophysis is controlled by nerve stimulation.
Hormones of Anterior lobe of the Pituitary gland (Adenohypophysis):
1. GH - Stimulates the growth of bones, muscles, and other organs.
2. TSH - Stimulates the thyroid glandular cells to produce Thyroid hormones.
3. ACTH - Stimulates the adrenal cortex to produce corticosteroids.
4. FSH & LH - Promote the growth of gonads (ovaries and testes) and stimulate them to produce sex hormones (Testosterone in males & Estrogen and Progesterone in females).
5. Prolactin - Promotes the development of glandular tissue in female breasts during pregnancy and stimulates milk production after the birth of the infant.
Hormones of Posterior lobe of the Pituitary gland (Neurohypophysis):
1. ADH (Antidiuretic hormone) - Promotes reabsorption of water in the tubules of nephrons and prevents excess water loss through urine. Inadequate secretion of ADH leads to Diabetes Insipidus (increased output of urine).
2. Oxytocin - Stimulates uterine wall contraction and ejection of milk from lactating breast.
Thyroid gland: Avascular organ, located in the neck region, consists of 2 lobes, one on each side of the trachea.
Hormones of the Thyroid gland:
1. T3 & T4 - Increases the rate of metabolism and protein synthesis; accelerates growth; and stimulates activities of the Nervous system.
2. Calcitonin - Reduces the calcium levels in the blood.
Parathyroid glands: Four small masses on the posterior surface of the thyroid glands.
The hormone of Parathyroid glands: 1. Parathyroid hormone / Parathormone - Maintains normal levels of calcium in the blood.
Adrenal Glands: Adrenal or suprarenal glands are paired glands located on the upper portion of each kidney.
The hormone of Adrenal glands:
1. Hormones of Adrenal Cortex (Corticosteroids):
a. Glucocorticoids (Cortisol) - Aids in stress and metabolism.
b. Mineralocorticoids (Aldosterone) - Regulates electrolytes.
c. Gonadocorticoids (Androgens and Estrogens).
2. Hormones of Adrenal Medulla (Catecholamines/stress busters):
a. Epinephrine/adrenaline - Aids in stress.
b. Norepinephrine/noradrenaline.
Ovaries (female gonads): Two small oval/almond-shaped glands, located on either side of the uterus, produce female sex hormones.
Hormones of Ovaries:
1. Estrogen - Help in the development of secondary sex characteristics.
2. Progesterone - Causes uterine lining to thicken in preparation for pregnancy.
Testes (male gonads): Paired oval organs that lie in the scrotum, produce male sex hormones.
The hormone of Testes: 1. Testosterone - Stimulates the development of secondary sexual characteristics in males and enhances male sex drive.
Pancreas: A large gland situated behind the stomach. Pancreas Parts - Endocrine and Exocrine.
Endocrine Part of Pancreas: The endocrine part of the pancreas consists of pancreatic islets/islets of Langerhans, which have Alpha and Beta cells.
Alpha Cells - Secretes hormone Glucagon.
Beta Cells - Secretes hormone insulin.
Hormones of Endocrine Part of Pancreas:
1. Glucogan - Increases glucose levels in the blood.
2. Insulin - Decreases glucose levels in the blood.
Exocrine Part of Pancreas: Exocrine part produces pancreatic juices and enzymes to digest food. Pancreatic juices and enzymes pass through the pancreatic duct to the duodenum.
Islet of Langerhans: Cellular masses throughout the pancreas, secrete insulin necessary to control carbohydrate metabolism.
Pineal gland: Pea shaped gland in the brain. Help in regulating hormones exp melatonin.
A hormone of the Pineal gland: 1. Melatonin - Promotes sleepiness and helps regulate the body's biological clock.
Hyposecretion (an endocrine disorder): Deficient hormone production by an endocrine gland.
Types of Hyposecretion:
1. Primary Hyposecretion (deficient hormone production due to the abnormality in the gland itself).
2. Secondary Hyposecretion (deficient hormone production is due to the abnormality in the Pituitary gland).
3. Tertiary Hyposecretion (deficient hormone production is due to the abnormality in the Hypothalamus).
Hypersecretion: Excessive secretion of the hormone by an endocrine gland.
Types of Hypersecretion:
1. Primary Hypersecretion (deficient hormone production due to the abnormality in the gland itself).
2. Secondary Hypersecretion (deficient hormone production is due to the abnormality in the Pituitary gland).
3. Tertiary Hypersecretion (deficient hormone production is due to the abnormality in the Hypothalamus).
Endocrinologist: A physician who specialized in Endocrinology.
Polydipsia: Excessive thirst.
Goiter: Due to Iodine deficiency enlargement of the thyroid gland.
Hyperthyroidism: Overactivity of the thyroid gland.
Hypothyroidism: Underactivity of the thyroid gland.
Thyroid carcinoma: Cancer of the thyroid gland.
Hyperparathyroidism: Excessive production of parathormone.
Hypoparathyroidism: Deficient production of parathormone.
Adrenal virilism: Excessive output of adrenal androgens.
Hyperinsulinism: Excessive secretion of insulin (causing hypoglycemia).
Hyperinsulinism: Lack of insulin secretion.
Gigantism: Hypersecretion of GH in children leading to abnormal growth of the body.
Dwarfism: Hyposecretion of GH in children leading to short stature.
Panhypopituitarism: Deficiency of all pituitary hormones.
Hypercalcemia: Excessive amounts of calcium in the blood.
Hyperglycemia: Excessive amounts of sugar in the blood.
Hyperkalemia: Excessive potassium in the blood.
Hypoglycemia: Deficiency of sugar in the blood.
Hyponatremia: Deficiency of sodium in the blood.
Diabetes Mellitus: Disorder of carbohydrate metabolism, under activity of the Islets of Langerhans results in low insulin production.
Diabetes Insipidus: Inadequate secretion of ADH leads to Diabetes Insipidus (increased output of urine).
Adrenalectomy: Excision of the adrenal gland.
Parathyroidectomy: Excision of the parathyroid gland.
Thyroidectomy: Excision of the thyroid gland.
Thyroparathyroidectomy: Excision of the thyroid and parathyroid glands.
Acromegaly: Excessive secretion of growth hormone by the pituitary gland, as a result, enlargement of the peripheral parts of the body.
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